Responding to Ms Harman's question on EU treaty change, David Cameron says what matters is making sure there is "agreement on the substance of the changes" that the UK is seeking, that involve treaty change. "That is what we hope to achieve," he adds.

Bringing her remarks to a close, Ms Harman says that the UK may be an island, but "this week's terrible events remind us once again that we are all interconnected". Mr Cameron, responding, thanks her for her remarks.

On the PM's EU reform bid, Harriet Harman asks David Cameron to confirm that there will be no change to the EU's treaties ahead of the in/out vote by 2017 . She tells the House: "Of course negotiations are sensitive but it's evident that even the people he is negotiating with are not entirely clear what he is negotiating for," she says, and claims that neither are the British people.

Turning to the EU, Harriet Harman sounds a warning about the potential impact of a Greek exit from the euro on Britain. Addressing the problem of migration, she says the UK should offer to help refugees who have fled from persecution.

The acting Labour leader says the death toll in Syria and Iraq continues to rise "relentlessly", and cites the recent terror attacks last Friday. She presses the prime minister for more information on the international efforts to prevent the spread of terrorism.

"This violence stems from an extremist ideology which hijacks the religion of Islam", Ms Harman says, and adds that the UK must be resolute in standing up for values, such as peace, freedom of speech and equality.

We know from the 7/7 London bombings that support will be needed for the bereaved and injured in the months and years to come, she says, and calls for a dedicated taskforce to ensure this.

Image source, PA

Time for acting Labour leader Harriet Harman to respond to the PM's statement. She offers the House's heartfelt condolences to the relatives and friends of those killed in the Tunisian beach attack. "We can't begin to understand what they must be going through," she says. Ms Harman thanks the PM for updating the House on the UK's response.

On his EU reform objectives, David Cameron says formal talks have now begun and will be reconsidered at the next summit in December. The talks will take "tenacity and patience" but change is possible - shown by his attempt to cut the EU budget in the last Parliament, he says. 

Turning to the European Council summit, David Cameron is setting out what steps were taken by European leaders to tackle the Mediterranean migrants crisis. He says that focusing primarily on setting up a relocation scheme would be "counter-productive" as it makes the "smugglers' business model" more attractive - rather than breaking it. The UK will not take part, but will enhance plans to resettle the most vulnerable refugees from outside the EU, particularly from Syria, he adds.

The House is listening in respectful silence as David Cameron makes his statement on the floor of the Commons. He tells the chamber that British security services will carry out a major anti-terror training exercise in London this week, to test capabilities.

The prime minister pays thanks to the Tunisian authorities for their assistance throughout this "horrific ordeal". On the Foreign Office's travel advice, he says it will not be advising against visiting Tunisia resorts. These are difficult judgements, he tells MPs, but he adds: "Until we've defeated this threat we must resolve as a country to carry on living our lives alongside it."

David Cameron says all of last Friday's terror attacks - in Tunisia, France and Kuwait - were driven by the same "perverse ideology", but he says there is no evidence to suggest that they were directly co-ordinated. He is now citing what steps the UK is doing to help those affected by the attack in Tunisia, and confirms that the Royal Air Force will repatriate all deceased, if their loved ones so wish.

David Cameron says at least 18 British nationals were killed in last Friday's Tunisian terror attack, with the death toll likely to rise further. These were innocent people, he says, and offers his condolences to their friends and families. He announces that there will be a national one-minute silence on Friday.

Image source, PA

The Labour Party has said the government needs to make it clear it has no intention of dropping the Olympics Games from the protected events list, after Eurosport was awarded the European television rights for the games for 2018-2024. 

Shadow secretary of state for culture, media and sport, Chris Bryant, also called on Eurosport to clarify its plans for UK coverage "as a matter of urgency".  

Mark Urban
Newsnight Defence and Diplomatic Editor

The prime minister's promise of a "full spectrum" response to the Tunisian and other recent terror attacks is not new thinking but reflects a long held view that the response to violence must be comprehensive in its approach. It eschews the tabloid palliative of the "send in the SAS" and acknowledges the need to look at a broad range of activities ranging from immigration controls, security precautions, and support to foreign governments to battling militant ideology.

Read more here.